1. Field of the Invention
The present invention relates to a new and improved device for reading, modifying and writing information on a storage medium, and more particularly to a method and apparatus for authenticating the medium and information stored on the medium by performing spatial measurements using a divided track transducer head.
2. Description of the Related Art
In many instances, it is desirable to provide a method and apparatus for storing and transporting information. In particular, many ways have been devised for encoding information on a medium which can be conveniently carried about by a person during the normal course of business. For example, credit cards, debit cards, electronic purse cards, decrementing value cards, checks, driver""s licenses, identification cards, access control cards, magnetic tapes and disc, and many other such media which are small enough to be conveniently carried in a person""s handbag or wallet are ubiquitous today. However, in many of the applications in which these media are intended to be used, security is an important concern. That is, it is important that only authorized organizations are capable of modifying the information stored thereon. One very common way for information to be stored on such a medium is by magnetically encoding the information.
Techniques for encoding information on magnetic media have been available for many years and are now relatively inexpensive. Other techniques include optical storage techniques and printed information using relative light and dark areas, such as the uniform purchasing codes (UPCs) which are printed on the packaging of most products today. For simplicity sake, only magnetic techniques are discussed in detail. However, it will be understood that the following discussion applies equally well to other techniques for storing information.
Cards which have a magnetic stripe attached thereto are ubiquitous in modem society. That is, nearly everyone carries one of the following cards, each of which typically has a magnetic stripe attached thereto: credit cards, bank cards (ATM cards), debit cards, identification cards, driver""s licenses, security access cards, check cashing cards, etc. Data is typically represented on magnetic medium by polarizing magnetic particles of the magnetic medium in one of two magnetic states. When magnetic medium is swiped across an inductive read head the moving magnetic field induces a magnetic field in the head core structure which in turn induces an electric current in the head read coil.
Alternately the change in magnetic field states can be directly measured using a magnastritive (MR) head. Either voltage waveform is converted to pulses with a peak detector. When reading the data from the magnetic medium, transitions between the two magnetic field states induce a voltage in the magnetic head read coil. A peak detector circuit translates this voltage into binary states. The head coil voltage is amplified by a differential amplifier then a dual edge peak detector switches between ground and VCC states each time the input changes polarity. The output of the peak detector is buffered by comparator with hysteresis to improve noise immunity. The states generated are detected as pulse durations; one pulse duration is approximately double in length to the other. The longer pulse duration represents a bit cell time and data value of zero, two consecutive pulse of the shorter duration also represent bit cell and in this case a data bit value of one.
Magnetically encoded information can easily be copied or transferred from one magnetic information storage medium to another. Unless special provisions are made to secure the information, information can be altered and re-encoded back onto the original medium or a duplicate of the original medium. If the information is used in a system for organizing financial transactions or for personal identification, then such copying, altering, and duplicating makes the person for whom the information was intended, and the organization who operates the system, vulnerable to fraud.
For example, if a magnetic stripe affixed to a debit card is used to indicate how much money is currently in a personal account, modifications to that information can be used to increase the apparent balance in order to purchase goods which have a higher value than actually exists in the account. Additionally, if the card is duplicated, the same account could be used by more than one person. It should be clear that fraud could occur in a number of ways if sensitive information is not properly secured. In fact fraud due to copying and modification of information magnetically encoded on portable media, such as magnetic stripe cards, is growing at an alarming rate. For example, it is estimated that the cost of fraud to the credit card industry alone will exceed one billion dollars per year before the end of the century.
A number of techniques have been proposed to authenticate both the information, and the medium on which the information is stored (commonly referred to as a xe2x80x9cdocumentxe2x80x9d), in order to prevent fraud. For example, U.S. Pat. No. 4,023,204 issued to Lee, discloses using a unique magnetic coating with pre-determined alignment of the magnetic particles as the basis for authentication measurements. Thus, a code which can not be altered can be implanted into the document to authenticate the document. U.S. Pat. No. 5,336,871 issued to Colgate, discloses the use of a hologram to authenticate a substrate on which a magnetic stripe is affixed. U.S. Pat. No. 5,354,097 issued to Tel, discloses the use of overlays to authenticate information.
U.S. Pat. No. 4,628,195, issued to Baus, discloses generating a security code number determined by the relative spatial positions of corresponding data in two different forms of encoded data on a card. In particular, Baus discloses using a conventional magnetic stripe as the first means for encoding data, and using embossed characters as a second means for encoding data. The relative position of the magnetic information with respect to the embossed information is used ti) generate a numeric security code. In addition, dyes or absorbers incorporated in a magnetic stripe have been used to attempt to encode a security identifier into the document on which the information resides.
However, each of these methods requires the use of special materials in the security process. Accordingly, none of the old documents would be usable, and all of the documents currently in use would have to he recalled and reissued using the new security process. Recalling and replacing all of the documents that are currently in use would be very costly and has hampered the widespread implementation of such technologies.
In the case of the technique disclosed by Baus, both an automatic reading method for reading the magnetic stripe, and also an automatic reading method for reading the embossed characters, are required. Therefore, there are two sub-systems required by this technique. Furthermore, readers used at the point-of-sale must preserve the spatial relationship between the magnetically stored information and the embossed characters. This is a cumbersome and expensive process which is very difficult to perform at the point-of-sale. Accordingly, it may be difficult to maintain reliable operation of systems which conform to the Baus technique.
Others have attempted to overcome the above limitations when the document is a magnetic medium by employing characteristics of the magnetic signals used to store the information to authenticate both the document and the information stored thereon. For example, U.S. Pat. No. 4,837,426 issued to Pease, discloses a method for authenticating documents by analyzing the amplitude of the magnetic signals. U.S. Pat. Nos. 5,408,505 and 5,428,683, each issued to Indeck, et al. disclose a method for authenticating documents using xe2x80x9cnoisexe2x80x9d in the saturation region of the magnetic data. U.S. Pat. Nos. 5,235,166, and 5,430,279, each issued to Fernandez, and U.S. Pat. No. 5,254,843 issued to Hynes, each disclose a method of authenticating documents by deriving inherent temporal measurements of timing variations of the data in the reading process.
All of the above mentioned methods for authenticating documents and information using characteristics of the magnetic signals have a common drawback in that variations in the motion of the document through the reading device cause variations in the characteristics used to authenticate the document, and therefore, result in errors in the authentication process. Furthermore, degradation of the reading device and the document over time due to natural wear causes the characteristics to either change, or to appear to change, causing further errors in the authentication process.
Accordingly, it would be desirable to provide a system which: (1) is capable of authenticating documents and the information stored thereon without use of a new material or process for generating the document to be authenticated; (2) is unaffected by changes in the speed at which the document moves with respect to the reader; and (3) will remain reliable over time.
In addition to the problems associated with authenticating documents and the information that is stored thereon, there is a need for methods for increasing the amount of information that can be stored on a document. For example, a magnetic stripe of a credit card is a relatively small area on which information can be stored. Accordingly, it would be advantageous to provide a method land apparatus which increases the amount of information that can be stored on a document.
Still further, in order to maintain standards for writing information on documents, it would be advantageous to be able to accurately determine the absolute distance between a transition in the information stored on a document from a first logical state to a second logical state without the need to control the velocity of the reader with respect to the document. The conventional method to accomplish this is with a precision peak detector which optimizes the peak detecting capabilities of conventional peak detector and using a constant speed drive transport.
Another method to accomplish this, as described in U.S. Pat. No. 5,770,846 issued to Mos et al., is with the use of a multiple gap magnetic head which detects adjacent bit transitions simultaneously. This method removes the requirement of a constant speed transport and still requires the use of precision peak detectors.
A new method of determining the placement of the data transitions without a peak detector is by measuring the frequency components of each bit cell with a Fourier or related transform. With this method of detection if two major frequency components occur, at F and xc2xd F the cell represents a data bit value of one. If only a single component is present at the lower frequency a cell data value of zero is decoded. The frequency components can be converted back to the time domain to accurately measure the distance between the points of interest.
With conventional magnetic stripe decoding there can be up to 14% variation in the ideal placement and actual detection of the bit-to-bit magnetic transitions. This variation along with the inability to sense an adjacent bit transition while writing data requires that conventional data writing write the complete track of information. When modifying data accurately measuring the placement is required to insure that the combined inaccuracies of the modified transitions and the initial placement is still within the 14% specification.
In U.S. Pat. No. 5,780,828 issued to Mos et al., there is described a method to selectively modify data without the requirement of writing a complete track of data. The method involves a two gap magnetic read head separated a know distance from a magnetic write gap. With the multiple read gaps separated by an odd multiple of bit transition spacing a write clock synchronized to the data can be generated.
This invention is a method and apparatus for reading and writing conventional ISO 7816 data with additional precisely placed pulses that appear as noise to conventional reading apparatuses and as data to the described invention using a combined spatial read/write head with a self-clocking data pattern, such as the Aiken code. In accordance with this invention, the velocity of the write head need not be constant with respect to the medium during the write operation. A write clock is generated by off setting two read heads by a known distance and using an integral write head to selectively modify the data.
Accordingly, a write clock can be generated from data, which is already present on the medium. Furthermore, by employing the split head spatial read/write head the data can be made secure from various sources of duplication including skimming. These observations are embodied in this invention as described below.
A number of embodiments of this invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Still further, it should be understood that while this invention is described in the context of a magnetic medium and magnetic read and write heads, this invention is applicable to any means for reading and writing data in which an Aiken code may be used. For example, such means might be bar codes written on paper, optically encoded data, etc. In yet another alternative embodiment of this invention, the read and write heads might move with respect to the medium. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the spirit and scope of the appended claims.
Therefore, the principal object of the present invention is to provide a new and improved method of encoding data on a medium.
It is a further object of the present invention to provide a new and improved method of reading data on a medium.
It is further object of the present invention is to provide new and improved method of securely encoding data on a medium compatible with conventional readers for non secured data.
It is a further object of the present invention to provide new and improved method of securely encoding data on a medium incompatible with conventional readers.
It is a further object of the present invention to provide a combination of functions of the above invention to provide greater utility than the individual functions support.
It is a final object of the present invention to improve and expand the capabilities of the conventional apparatuses used for reading and writing ISO 7816 data.
Briefly, the value-added data access that is the subject matter of the instant invention as described herein more specifically addresses a method and apparatus for placing and later determining the distance between transitions from a first logical state to a second logical state stored on a medium, for example, a document. This determination is used to precisely characterize the information pattern in order to authenticate the information and the medium on which the information is stored. The invention uses a reader having a leading and trailing read apparatus, which allow information to be read simultaneously from two or more locations spaced a known distance apart. The distance between the center lines of each read apparatus is preferably an odd integer multiple of one half the distance between logical clock transitions. The distance between a first transition at the leading read apparatus and a next transition at the trailing read apparatus is used as a reference, hence given the term the xe2x80x9cReference Valuexe2x80x9d. The Reference Value is compared with the distance between the first transition and a second transition on the medium. Detection of deviations in spacing between transitions is unaffected by variations in the velocity of the medium with respect to the reader.
Therefore, the present invention is a method and apparatus for reading and writing conventional ISO 7816 data with additional precisely placed pulses that appear as noise to conventional reading apparatuses and as data to the described invention. In addition the present invention applies to a medium, which moves at an uncontrolled velocity relative to a read/write apparatus with which the data is read and written.